Research On Broadbandization And Miniaturization Of Quadrifilar Helix Antenna

Satellite navigation and positioning system is playing a more and more important role in human daily life as the fast development of modern wireless communication. GPS (Global Positioning System) is widely used in civilian and army use. Recently, GPS technology has been developed enormously in civilian use, especially in vehicle navigation and mobile phone positioning. So, it is very important for us to do some research on the satellite navigation and positioning system antenna especially on the broadbandization and miniaturization technology. The quadrifilar helix antenna satisfies the requirement of satellite navigation and positioning system antenna for its wide beam and good circularly polarized characteristics. Three kinds of circularly polarized helix antennas for satellite navigation and positioning systems are presented in this thesis. The theory, detailed processes of designs and experimental results are introduced. This thesis mainly colludes the following four parts:Firstly, the pervious progress and present situation of the satellite navigation and positioning system are surveyed. The main antenna style and technology target are discussed. The characteristics of the microstrip antenna and the quadrifilar helix antenna are compared.Secondly, the structure and theory of the quadrifilar helix antenna are presented. The development of broadbandization and miniaturization technologies is summarized.Thirdly, a new design wideband core quadrifilar helix antenna is presented. The antenna which is feed by a Wilkinson divider and two wideband microstrip balun operates at the center frequency of 1575MHz and right hand circular polarization. The commercial software Ansoft HFSS 11.0 is used to analyze the radiation characteristics of the proposed quadrifilar helix antenna, such as axial-ratio, return loss and radiation pattern. The 3dB axial-ratio beamwidth and half power beamwidth reach 150 degrees, and the bandwidth is from 0.82GHz to 2.62GHz.Fourthly, a wideband core printed quadrifilar helix antenna with a novel conformal feeding network is presented. The simulated results show that the half power beamwidth and 3dB axial-ratio beamwidth reach 150 degrees. The antenna achieve a bandwidth of 39.7% for S11＜-10dB and a 3-dB axial-ratio bandwidth of about 22%. Another novel compact printed quadrifilar helical antenna with the same type feeding network is presented too. The installed place and the size of antenna are much reduced by using conformal feeding network and folded arms. The antenna can achieve an impedance bandwidth of 10.5% for S11＜-10dB and a 3dB axial-ratio bandwidth of 10.5%.The simulated results and measured result are presented and in good agreement.